Thermostat with bimetal set in plastic



Sept. 8, 1964 G. F. DALES 3,148,253

THERMOSTAT WITH BIMETAL SET IN PLASTIC Filed Sept. 26, 1961 f f l /2FIG. 9 -F|G.|O

INVENTOR.

7 8 GEORGE FRANKLIN DALES ATTQRNE 3 narily metallic, but may be plasticor of other 1 material. the holding means is sealed is out dust anddirt.

United States Patent Ofi ice 3,148,258 THERMOSTAT WITH BliMETAL SET INPLASTIC George Franklin Dales, 253 Castte Blvd, Akron, Ohio Filed Sept.26, 1961, Ser. No. 143,516 5 Claims. (Cl. 209-138) This inventionrelates to a thermostat which includes two electrodes adapted to makeand break contact. At least one of these electrodes is bimetallic. Theuse of an electrode composed of a non-bimetallic member with abimetallic member adjacent to it so that the bimetallic member moves thenon-bimetallic member is the equivalent of a bimetallic electrode forthe purpose of this patent.

The two electrodes are held in place by holding means which is composedat least in part of a set plastic. In use, the electrodes of thisthermostat may be immersed in a liquid, or air, or other gas, and areheated thereby so that the contacts are brought together and separatedas the medium in which they are immersed is heated or cooled, or viceversa. The electrodes are preferably enclosed in a casing of anystructure and shape which protects them from dust and dirt, and then theoperation of the thermostat is dependent upon the temperature within thecasing. The casing may or may not be a dielectric.

The two electrodes may both be bimetallic. Alternatively, one may bebimetallic, and the other non-bimetaL lie. The electrodes referred toherein as bimetallic, may be bimetallic only in part. Thus the portionin and above the holding means may advantageously be made nonbimetallicso that it does not flex as the temperature changes; and all or part ofthe remainder may be bimetallic. For certain operations a stop,preferably adjustable, is provided for one or even both of theelectrodes to establish the maximum distance that that electrode may bemoved away from the other electrode. The preferred type of thermostat inwhich such an arrangement is used is one in which the holding means issealed or otherwise held in one end of a tubular casing and a setscrewthreaded through the wall of the casing applies pressure to anelectrode. This casing may be cylindrical or of any other shape. It maybe seamless. It is ordidielectric The end of the casing opposite thatinto which preferably closed to keep The thermostat is ordinarily small,the electrodes ordinarily not being over one inch, or two inches inlength.

{If a casing is employed, the outside diameter of the easing need not beany greater than about may be larger.

The thermostat is advantageously employed in a cycle switch ortime-delay switch in which case it is preferably enclosed in a casingand the casing is provided with a resistance member which may bearranged in parallel with the line or load, or in series with the loadas will be more particularly described in what follows.

The holding means in which the electrodes are held includes a rigiddielectric material which serves as a fulcrum. Ceramics, plastics,fiberboard or other rigid sheet materials may be employed, and whateverthe composition of the sheet material, it forms a snug fit with the oneor more electrodes. A limp paper or the like may be used if it isrigidified by the set plastic. This dielectric material is preferablyheld in one end of a short sleeve and the sleeve is filled with theplastic. The plastic may be supplied in a molten condition, or it may bein the form of solid particles, such as beads or powder, whenincorporated in the thermostat, and then heated. If the plastic '3chemically or thermally curable, the contact points of /8 inch, but

the electrodes are brought together or spaced to make and 3,148,258Patented Sept. 8, 1964 break contact at any predetermined temperatureand the plastic is heated to this temperature. If the plastic is notcurable, but sets when cooled from being in the molten state, thetemperature at which it sets is predetermined and the electrodes are setin it at thi temperature with the contact points together, or spaced apredetermined distance so that they are brought together or separated(as the case may be) when the thermostat is heated to this temperaturewhen in use.

The plastic may be one of those which sets at a predeterminedtempera-ture, described in Coates U.S. 2,745,- 924. The plastic maycontain an inert filler. The gasket of Coates was actually a temporarysilicone sponge which was removed in the final form of the thermostatshown in FIGURE 10 of the patent.

The invention will be further described in connection with theaccompanying drawings, in which- FIG. 1 is a side view of one form ofthermostat;

FIG. 2 is a side View of a similar form of thermostat employing aslightly modified sleeve;

FIG. 3 is a View in section of the thermostat of PEG. 1 in a casing;

FIG. 4- is a view in section of the thermostat of FIG. 2 in a casing;

FIG. 5 is a view in section of a thermostat in a casing with a setscrewadjustably held in contact with one of the electrodes;

FIG. 6 is a view of a resistance wound casing containing an electrodewith a setscrew bearing against a different portion of one of theelectrodes;

FIGS. 7, 8 and 9 show schematically three views which illustrate themethod of producing the thermostat; and

FIG. 10 illustrates the use of a spacer between two electrodes while theplastic sets.

In the thermostat of FIG. 1, the two electrodes 1 and 2 may both bebimetallic. Alternatively, one may be bimetallic and the other may benon-bimetallic. Either one or both may comprise a non-bimetallic memberoperated y the pressure of an adjacent bimetallic member. The twoelectrodes are held in the holding means 4. This comprises a rigiddielectric sheet material 5 which may be fiberboard or the like. Thereare two openings 6 and 7 in the sheet 5 in which the respectiveelectrodes are held. The sheet makes a snug fit with the electrodes sothat as the temperature of the thermostat is changed and the contactpoints move toward and away from one another, they fulcrum on at leastone of the opposite edges of the openings 6 and 7 in the sheet. If thebuttons are held together by pressure applied to the electrodes abovethe contact buttons when the plastic is set, the electrodes fulcrum onthe edges of the narrow portion of the fulcrum between the openings 6and 7. If the pressure is applied to the electrodes beyond the buttons,they fulcrum on the two outside edges of the openings 6 and 7.

The outside periphery of the sheet material 5 conforms to the insideperiphery of the sleeve 9. This sleeve may be circular, square,octagonal, or any shape. The sleeve is filled with a set plasticmaterial 10. Preferably the sleeve is held upright with the sheetmaterial 5 at the bottom and then filled with plastic which may bemolten or in a finely divided solid state. The electrodes are held inany predetermined relation with one another so that they will make orbreak contact at a given temperature. They are held in this positionwhile the plastic sets, and thereafter the thermostat will function atthe predetermined temperature. Any means may be employed for holding theelectrodes while the plastic is setting. These electrodes may bestraight or of any desired shape, and they need not necessarily beparallel as illustrated in FIG. 1.

If a curable resin is a liquid or a solution, but it may be supplied ina finely divided solid state and then be melted or dissolved beforebeing set chemically or thermally. A preferred curable resin is anepoxide which is supplied as a liquid containing an activator whichcatalyzes polymerization when the mixture is heated to any temperaturewithin a wide range. When polymerized the resin sets as a solid. A coldsetting resin may be used if the thermostat is to be actuated at a lowtemperature. The thermostat is heated and maintained at a predeterminedtemperature while the resin becomes solid. It is prearranged that either(1) the electrode buttons are in contact at this temperature (in whichcase the thermostat is operable at this temperature later when put touse), or (2) the electrode buttons are spaced a predetermined distanceat this temperature, as by insertion of a spacer of predeterminedthickness between them (in which case the thermostat is thereafteroperable at a predetermined temperature above or below this temperaturedepending upon how far the electrodes are spaced when the resin is setand (12) upon whether the electrodes are arranged to come into contactor separate when heated).

If the resin is a thermoplastic which has no cold flow, such as a glass,it will have a known solidification temperature. For instance, thecomposition of certain glasses is kept so constant that thesolidification point does not vary more than two degrees from batch tobatch. If the plastic solidifies at the temperature at which thethermostat is to be actuated, the buttons are held together while theplastic solidifies. If the thermostat is to operate at a temperaturedifferent from that at which the plastic solidifies, the buttons arespaced a predetermined distance while the plastic solidifies, such thatthe buttons will thereafter be in contact at the desired operatingtemperature.

If the dielectric sheet is porous (whether a fiberboard, glass fibersheeting or other composition), it may be flexible or even limp in itsoriginal condition, and become impregnated by the liquid plastic aboveit. The sheet will then become rigid enough to serve as a fulcrum whenthe plastic sets.

The thermostat of FIG. 1 may be used in the condition shown, or it maybe encased in any suitable casing to keep out dust and dirt. It may beheld in an opening in an engine block. It may be spot welded in positionor held by any other means.

The electrode of FIG. 2 is identical in design except that when theelectrode is erect, the dielectric sheet 5 is supported by the inturnedflange ha of the sleeve. The opposite end of the flange is turnedoutwardly at 91). It may thus be supported in an opening and held inplace as by screwing a setscrew or cap screw into a threaded openingadjacent to it so that the head of the screw is brought into pressurecontact with the metal of the holding means. The flange 9b might beturned inwardly over the plastic content of the holding means, ifdesired.

The thermostat is preferably held in a casing 12 (FIG. 4) and the casingmay have a circular, square or octagonal section, or be of any otherdesired shape. It may be of metal or plastic, or of any other desiredcomposition. It may be closed at the end 13, but this is not necessary.The holding means 4 is fastened in the easing, preferably at one end. Ifthe sleeve 9 and casing 12 are both metallic the holding means 4 may beheld in position by spot welding. Other means for holding the thermostatin the casing may be employed, and if the casing is of metal and thesleeve is plastic, other means than spot welding will be required aswill be evident to the man skilled in the art.

FIGURE 4 shows the thermostat of FIG. 2 in the casing 12 with the flange9b of the sleeve over the open end of the casing. If the sleeve andeasing are of metal, the flange may be welded to the end of the casing.The thermostat may be held in the casing by an desired means.

FIGURE 5 shows a thermostat located in a casing with nation with theplastic.

an adjusting screw 15 threaded into one wall of the casing and bearingagainst one of the electrodes 16. Both electrodes may be bimetallic,although the electrode 16 may be non-bimetallic and the electrode 17bimetallic. (As previously stated, an electrode composed of a bimetallicmember pressing against a non-bimetallic member is the equivalent of thebimetallic electrodes to which reference is made in this specification.)

A setscrew may be utilized to adjust the temperature at which thethermostat will operate temporarily. After the temporary period haspassed the setscrew can be screwed out of contact with the electrode sothat the thermostat will again operate at the predetermined temperature.

The position of the setscrew 15 in the casing may be varied, and thepitch of the threads may be varied. A setscrew provided with a dial headwith temperature markings, without indicating whether the scale iscentigrade or Fahrenheit, can be used for adjustments on both scales bylocating the setscrew nearer or farther from the holding means. Thesetscrew 15 is preferably made of non-conducting material or, if ofconducting material, it may be held in a non-conducting bushing held inthe opening in the casing. Alternatively, the setscrew 15 may becomposed of conducting material with a dielectric end in contact withthe electrode 16. There may be situations where the setscrew may be ofconducting material connecting the casing electrically with theelectrode 16.

Any of the electrodes previously described may be employed as a switchas illustrated in FIG. 6. Here the casing is Wound with a resistancewhich is parallel to the line, or parallel to the load, or in serieswith the load as will be explained in what follows. The thermostat neednot be in a casing to operate as a switch, and the resistance need notencircle the thermostat. The two may be side by side, provided heat fromthe resistance is adequate to open and break the contacts of thethermostat.

In FIG. 6 the casing 12 is Wound by the resistance wire 2%, and theterminals of the resistance wire are connected with the electricalconnections 21 and 22. If the casing 12 is made of metal a layer ofinsulating material 23 separates the resistance from the casing. Theresistance may be a coil of wire, a tape, or the like. This resistancemay be connected into the thermostat circuit in ways known to the art.

FIGURE 6 shows a setscrew 25 located to contact one of the electrodes atthe contact points. It is not necessary that the thermostat used as aswitch include any setscrew. The setscrew is shown to illustrate thelocation of the,

setscrew in a different position from that shown in FIG.

5. A setscrew may be used with a thermostat employed as a switch whenlocated in any position, but the use of a setscrew is not necessary. Twosetscrews may be em ployed, each limiting the distance one of theelectrodes may move away from the other electrode, but the use of twosuch setscrews will not be usual.

FIGURES 7, 8 and 9 illustrate schematically the method of forming thethermostat. Reference will be had more particularly to the thermostatshown in FIG. 1, but it is to be understood that this is illustrativeand that other types of electrodes may be used and other holding meansmay be formed about the electrodes.

FIGURE 7 shows the first step of the process in which the electrodes 1and 2 are arranged side by side with the contact points opposite oneanother. They are held in this manner by any suitable dielectric means.FIGURE 7 shows the dielectric sheet 5 which may be fiberboard, aphenol-formaldehyde resin, asbestos, or other dielectric which ispreferably rigid enough to support itself and serve as a fulcrum,although it is quite satisfactory to use a sheet which is less rigid andthen stiffen it by impreg- FIGURE 8 shows the sheet 5 in the sleeve 9.It may first be inserted in the sleeve, before or after placing theelectrodes in the openings in it. The openings are preferably of justthe same shape and size as the section of the electrodes so that theelectrodes fit snugly in the openings. (In FIGS. 7-9 the size of theopenings is exaggerated to illustrate the operation.)

The electrodes are then embedded in a plastic 10, and unless theelectrodes are insulated, this plastic is a dielectric. The sleeve 9serves as a retaining wall and the plastic is built up toward the outerends of the electrodes, but in the final product, as illustrated in thedrawings, these ends project from the plastic. Although reference ismade herein to the electrodes projecting from the plastic, it is to beunderstood that leads or terminals may be Welded to the electrodes, orotherwise attached thereto, and the leads or terminals alone may projectfrom the plastic.

FIGURE 10 illustrates the use of a spacer 30 between two electrodes,which may be any two of the electrodes shown in the drawings. If theelectrodes are arranged to separate on heating, a spacer ofpredetermined width is used during calibration to separate the buttonson the electrodes if the plastic sets at a temperature above that atwhich the thermostat is to operate; and if the bimetal or bimetals arearranged so that the buttons come together on heating, a spacer ofpredetermined width is used during calibration to separate the buttonson the electrodes if the plastic sets at a temperature below that atwhich the thermostat is to operate.

The plastic is a settable plastic. It is liquid when it is formed aroundthe electrode, and thereafter it is allowed to set and harden. It may bea thermosetting resin of which there are many on the market, or it maymerely be a molten plastic which sets to a solid on cooling. Itpreferably is not a brittle type. It may be an asphaltic or resinousmaterial, and if resinous it may be synthetic. It may include chemicalswhich cause it to set. Ordinarily the plastic will be of an organiccomposition, but inorganic cements, etc. may be employed.

The electrodes are held gently in contact with one another or spaced apredetermined distance by a suitable fixture while the plastic issetting. Any suitable means for heating the electrodes to thetemperature of the plastic may be employed.

For purposes of illustration, it is to be understood that in the variousviews the plates 5 which hold the electrodes have a circular outline,and the sleeves are cylindrical, although it is to be understood thatthe shape of s the plate and sleeve is not a feature of the invention,and

they may be of any desired shape.

These small thermostats, whether encased or not, are

- Well adapted for use in the automatic control of the op- Reration ofvarious appliances such as ovens, wattle irons, electric ions, etc. Theyare particularly adapted for use b in appliances where a circuit is tobe interrupted, temporarily or permanently.

They may be used in connection with electrical heating means such asresistances which are located in heattransferring relation with thethermostat. These resistances are advantageously placed around athermostat located within a casing much as illustrated in FIG. 6,although other means of associating the resistance with the thermostatmay be employed. Different types of resistances may be used.

The drawings and descriptive matter are illustrative, and the inventionis covered in the claims which follow.

The invention is a continuation-in-part of my applications Serial No.728,484, filed April 14, 1958 (now abandoned), and Serial No. 31,962,filed May 26, 1960.

What I claim is:

1. A thermostat which comprises at least one bimetal electrode held in aset plastic with one end of the bimetal projecting from one surface ofthe plastic, which end is adapted to make and break contact with anotherportion of the thermostat on change in its temperature, a rigid fulcrumplate having constant dimensions within the expected ambient temperaturerange, said plate being in intimate contact with said surface of theplastic, and a hole in the plate with the electrode fulcrumed againstone edge of the hole.

2. A thermostat which comprises at least one bimetal electrode held in aset plastic, a rigid impregnatable fulcrum plate having constantdimensions within the expected ambient temperature range, at least onesurface of which plate is impregnated with the plastic, and a hole inthe plate with the electrode fulcrumed against one edge of the hole.

3. The thermostat of claim 1 which includes holding means and a casing,the plastic and fulcrum plate being within the holding means, and theholding means being held in one end of the casing.

4. The thermostat of claim 1 which includes holding means and a casing,the plastic and fulcrum plate being within the holding means with thefulcrum plate at one end thereof, the end of the holding means farthestfrom the fulcrum plate being flared out, and the casing being around theholding means with the flared-out end thereof against one end of thecasing.

5. The thermostat of claim 1 in which the plastic is glass which has nocold flow.

References Cited in the file of this patent UNITED STATES PATENTS

1. A THERMOSTAT WHICH COMPRISES AT LEAST ONE BIMETAL ELECTRODE HELD IN ASET PLALSTIC WITH ONE END OF THE BIMETAL PROJECTING FROM ONE SURFACE OFTHE PLASTIC, WHICH END IS ADAPTED TO MAKE AND BREAK CONTACT WITH ANOTHERPORTON OF THE THERMOSTAT ON CHGANGE IN ITS TEMPERATURE, A RIGID FULCRIUMPLALTE HAVING CONSTANT DIMENSIONS WITHIN THE EXPECTED AMBIENTTEMPERATURE RANGE, SAID PLATE BEING IN INTIMATE CONTACT WITH SAIDSURFACE OF THE PLASTIC, AND A HOLE IN THE PLATE WITH THE ELECTRODEFULCRUMED AGAINST ONE EDGE OF THE HOLE.